Heart FailureIf the heart is unable to pump an adequate amount of blood to the body, as in some people with AF, the body begins to compensate by retaining fluid. This can lead to a condition called heart failure. Heart failure results in the accumulation of fluid in the lower legs (edema) and the lungs (pulmonary edema). Pulmonary edema makes breathing more difficult and reduces the ability of the lung to add oxygen to and remove carbon dioxide from the blood. The levels of oxygen in the blood can drop, and the levels of carbon dioxide in the blood can rise, a complication called respiratory failure. This is a life-threatening complication.
StrokeQuivering of the atria in AF cause blood inside the atria to stagnate. Stagnant blood tends to form blood clots along the walls of the atria. Sometimes, these blood clots dislodge, pass through the ventricles, and lodge in the brain, lungs, and other parts of the body. This process is called embolization. One common complication of AF is a blood clot that travels to the brain and causes the sudden onset of one-sided paralysis of the extremities and/or the facial muscles (an embolic stroke). A blood clot that travels to the lungs can cause injury to the lung tissues (pulmonary infarction), and symptoms of chest pain and shortness of breath. When blood clots travel to the body's extremities, cold hands, feet, or legs may occur suddenly because of the lack of blood.
Tuesday, January 20, 2009
What is atrial fibrillation?
What is atrial fibrillation? Atrial fibrillation (AF) is the most common, abnormal rhythm of the heart.The heart contracts (beats) and pumps blood with a regular rhythm, for example, at a rate of 60 beats per minute there is a beat every second. The heart may beat faster or slower with a shorter or longer interval between beats, but at any one rate the interval between beats is constant. This regular rhythm occurs as a result of regular electrical discharges (currents) that travel through the heart and cause the muscle of the heart to contract. In AF, the electrical discharges are irregular and rapid and, as a result, the heart beats irregularly and, usually, rapidly.AF is common; half a million new cases are diagnosed yearly in the U.S., and billions of dollars are spent annually on its diagnosis and treatment.
What causes atrial fibrillation? Normal function of the heartThe heart has four chambers. The upper two chambers are the atria, and the lower two chambers are the ventricles. Blood returning to the heart from the body in the superior and inferior vena cava contains low levels of oxygen and high levels of carbon dioxide. This blood flows into the right atrium and then into the adjacent right ventricle. After the ventricle fills, contraction of the right atrium pumps additional blood into the right ventricle. The right ventricle then contracts and pumps the blood to the lungs where the blood takes up oxygen and gives off carbon dioxide. The blood then flows from the lungs to the left atrium and into the adjacent left ventricle. Contraction of the left atrium pumps additional blood into the left ventricle. The left ventricle then contracts and pumps the blood to the rest of the body. The heartbeat (pulse) that we feel is caused by the contraction of the ventricles.
The ventricles must deliver enough blood to the body for the body to function normally. The amount of blood that is pumped depends on several factors. The most important factor is the rate of contraction of the heart (the heart rate). As the heart rate increases, more blood is pumped. In addition, the heart pumps more blood with each beat when the atria contract and fill the ventricles with additional blood just before the ventricles contract.
With each beat of the heart, an electrical discharge (current) passes through the electrical system of the heart. The electrical discharge causes the muscle of the atria and ventricles to contract and pump blood. The electrical system of the heart consists of the SA node (sino-atrial node), the AV node (atrio-ventricular node) and special tissues in the atria and the ventricles that conduct the current.
The SA node is the heart's electrical pacemaker. It is a small patch of cells located in the wall of the right atrium; the frequency with which the SA node discharges determines the rate at which the heart beats. The electrical current passes from the SA node, through the special tissues of the atria and into the AV node. The AV node serves as an electrical relay station between the atria and the ventricles. Electrical signals from the atria must pass through the AV node to reach the ventricles.
The electrical discharges from the SA node cause the atria to contract and pump blood into the ventricles. The same discharges then pass through the AV node to reach the ventricles, traveling through the special tissues of the ventricles and causing the ventricles to contract. In a normal heart, the rate of atrial contraction is the same as the rate of ventricular contraction.
At rest, the frequency of the electrical discharges originating from the SA node is low, and the heart beats at the lower range of normal (60-80 beats/minute). During exercise or excitement, the frequency of discharges from the SA node increases, increasing the rate at which the heart beats.
Function of the heart during atrial fibrillationDuring AF, electrical discharges are not generated solely by the SA node. Instead, electrical discharges come from other parts of the atria. These abnormal discharges are rapid and irregular and may exceed 350 discharges per minute. The rapid and irregular discharges cause ineffective contractions of the atria. In fact, the atria quiver rather than beat as a unit. This reduces the ability of the atria to pump blood into the ventricles.
The rapid and irregular electrical discharges from the atria then pass through the AV node and into the ventricles, causing the ventricles to contract irregularly and (usually) rapidly. The contractions of the ventricles may average 150/minute, much slower than the rate in the atria. (The ventricles are unable to contract at 350/minute.) Even at an average rate of 150/minute, the ventricles may not have enough time to fill maximally with blood before the next contraction, particularly without the normal contraction of the atria. Thus, AF decreases the amount of blood pumped by the ventricles because of their rapid rate of contraction and the absence of normal atrial contractions.
Heart rate during atrial fibrillationIn a heart that is beating normally, the rate of ventricular contraction is the same as the rate of atrial contraction. In AF, however, the rate of ventricular contraction is less than the rate of atrial contraction. The rate of ventricular contraction in AF is determined by the speed of transmission of the atrial electrical discharges through the AV node. In people with a normal AV node, the rate of ventricular contraction in untreated AF usually ranges from 80 to 180 beats/minute; the higher the transmission, the higher the heart rate.
Some older people have slow transmission through the AV node due to disease within the AV node. When these people develop AF, their heart rates remain normal or slower than normal. As disease in the AV node advances, these people can even develop an excessively slow heart rate and require a permanent pacemaker to increase the rate of ventricular contractions.
What are the symptoms of atrial fibrillation?Many patients with atrial fibrillation have no symptoms and are unaware of the abnormal heart rhythm. The most common symptom of atrial fibrillation is palpitations, an uncomfortable awareness of the rapid and irregular heartbeat. Other symptoms of atrial fibrillation are caused by the diminished delivery of blood to the body. These symptoms include dizziness, fainting, weakness, fatigue, shortness of breath, and angina (chest pain due to reduced blood flow to the heart muscles).
What causes atrial fibrillation? Normal function of the heartThe heart has four chambers. The upper two chambers are the atria, and the lower two chambers are the ventricles. Blood returning to the heart from the body in the superior and inferior vena cava contains low levels of oxygen and high levels of carbon dioxide. This blood flows into the right atrium and then into the adjacent right ventricle. After the ventricle fills, contraction of the right atrium pumps additional blood into the right ventricle. The right ventricle then contracts and pumps the blood to the lungs where the blood takes up oxygen and gives off carbon dioxide. The blood then flows from the lungs to the left atrium and into the adjacent left ventricle. Contraction of the left atrium pumps additional blood into the left ventricle. The left ventricle then contracts and pumps the blood to the rest of the body. The heartbeat (pulse) that we feel is caused by the contraction of the ventricles.
The ventricles must deliver enough blood to the body for the body to function normally. The amount of blood that is pumped depends on several factors. The most important factor is the rate of contraction of the heart (the heart rate). As the heart rate increases, more blood is pumped. In addition, the heart pumps more blood with each beat when the atria contract and fill the ventricles with additional blood just before the ventricles contract.
With each beat of the heart, an electrical discharge (current) passes through the electrical system of the heart. The electrical discharge causes the muscle of the atria and ventricles to contract and pump blood. The electrical system of the heart consists of the SA node (sino-atrial node), the AV node (atrio-ventricular node) and special tissues in the atria and the ventricles that conduct the current.
The SA node is the heart's electrical pacemaker. It is a small patch of cells located in the wall of the right atrium; the frequency with which the SA node discharges determines the rate at which the heart beats. The electrical current passes from the SA node, through the special tissues of the atria and into the AV node. The AV node serves as an electrical relay station between the atria and the ventricles. Electrical signals from the atria must pass through the AV node to reach the ventricles.
The electrical discharges from the SA node cause the atria to contract and pump blood into the ventricles. The same discharges then pass through the AV node to reach the ventricles, traveling through the special tissues of the ventricles and causing the ventricles to contract. In a normal heart, the rate of atrial contraction is the same as the rate of ventricular contraction.
At rest, the frequency of the electrical discharges originating from the SA node is low, and the heart beats at the lower range of normal (60-80 beats/minute). During exercise or excitement, the frequency of discharges from the SA node increases, increasing the rate at which the heart beats.
Function of the heart during atrial fibrillationDuring AF, electrical discharges are not generated solely by the SA node. Instead, electrical discharges come from other parts of the atria. These abnormal discharges are rapid and irregular and may exceed 350 discharges per minute. The rapid and irregular discharges cause ineffective contractions of the atria. In fact, the atria quiver rather than beat as a unit. This reduces the ability of the atria to pump blood into the ventricles.
The rapid and irregular electrical discharges from the atria then pass through the AV node and into the ventricles, causing the ventricles to contract irregularly and (usually) rapidly. The contractions of the ventricles may average 150/minute, much slower than the rate in the atria. (The ventricles are unable to contract at 350/minute.) Even at an average rate of 150/minute, the ventricles may not have enough time to fill maximally with blood before the next contraction, particularly without the normal contraction of the atria. Thus, AF decreases the amount of blood pumped by the ventricles because of their rapid rate of contraction and the absence of normal atrial contractions.
Heart rate during atrial fibrillationIn a heart that is beating normally, the rate of ventricular contraction is the same as the rate of atrial contraction. In AF, however, the rate of ventricular contraction is less than the rate of atrial contraction. The rate of ventricular contraction in AF is determined by the speed of transmission of the atrial electrical discharges through the AV node. In people with a normal AV node, the rate of ventricular contraction in untreated AF usually ranges from 80 to 180 beats/minute; the higher the transmission, the higher the heart rate.
Some older people have slow transmission through the AV node due to disease within the AV node. When these people develop AF, their heart rates remain normal or slower than normal. As disease in the AV node advances, these people can even develop an excessively slow heart rate and require a permanent pacemaker to increase the rate of ventricular contractions.
What are the symptoms of atrial fibrillation?Many patients with atrial fibrillation have no symptoms and are unaware of the abnormal heart rhythm. The most common symptom of atrial fibrillation is palpitations, an uncomfortable awareness of the rapid and irregular heartbeat. Other symptoms of atrial fibrillation are caused by the diminished delivery of blood to the body. These symptoms include dizziness, fainting, weakness, fatigue, shortness of breath, and angina (chest pain due to reduced blood flow to the heart muscles).
High Blood Pressure (Hypertension) At A Glance
High Blood Pressure (Hypertension) At A Glance
High blood pressure (hypertension) is designated as either essential (primary) hypertension or secondary hypertension and is defined as a consistently elevated blood pressure exceeding 140/90 mm Hg.
In essential hypertension (95% of people with hypertension), no specific cause is found, while secondary hypertension (5% of people with hypertension) is caused by an abnormality somewhere in the body, such as in the kidney, adrenal gland, or aortic artery.
Essential hypertension may run in some families and occurs more often in the African American population, although the genes for essential hypertension have not yet been identified.
High salt intake, obesity, lack of regular exercise, excessive alcohol or coffee intake, and smoking may all adversely affect the outlook for the health of an individual with hypertension.
High blood pressure is called "the silent killer" because it often causes no symptoms for many years, even decades, until it finally damages certain critical organs.
Poorly controlled hypertension ultimately can cause damage to blood vessels in the eye, thickening of the heart muscle and heart attacks, hardening of the arteries (arteriosclerosis), kidney failure, and strokes.
Heightened public awareness and screening of the population are necessary to detect hypertension early enough so it can be treated before critical organs are damaged.
Lifestyle adjustments in diet and exercise and compliance with medication regimes are important factors in determining the outcome for people with hypertension.
Several classes of anti-hypertensive medications are available, including ACE inhibitors, ARB drugs, beta-blockers, diuretics, calcium channel blockers, alpha-blockers, and peripheral vasodilators.
Most anti-hypertensive medications can be used alone or in combination: some are used only in combination; some are preferred over others in certain specific medical situations; and some are not to be used (contraindicated) in other situations.
The goal of therapy for hypertension is to bring the blood pressure down to 140/85 in the general population and to even lower levels in diabetics, African Americans, and people with certain chronic kidney diseases.
Screening, diagnosing, treating, and controlling hypertension early in its course can significantly reduce the risk of developing strokes, heart attacks, or kidney failure.
High blood pressure (hypertension) is designated as either essential (primary) hypertension or secondary hypertension and is defined as a consistently elevated blood pressure exceeding 140/90 mm Hg.
In essential hypertension (95% of people with hypertension), no specific cause is found, while secondary hypertension (5% of people with hypertension) is caused by an abnormality somewhere in the body, such as in the kidney, adrenal gland, or aortic artery.
Essential hypertension may run in some families and occurs more often in the African American population, although the genes for essential hypertension have not yet been identified.
High salt intake, obesity, lack of regular exercise, excessive alcohol or coffee intake, and smoking may all adversely affect the outlook for the health of an individual with hypertension.
High blood pressure is called "the silent killer" because it often causes no symptoms for many years, even decades, until it finally damages certain critical organs.
Poorly controlled hypertension ultimately can cause damage to blood vessels in the eye, thickening of the heart muscle and heart attacks, hardening of the arteries (arteriosclerosis), kidney failure, and strokes.
Heightened public awareness and screening of the population are necessary to detect hypertension early enough so it can be treated before critical organs are damaged.
Lifestyle adjustments in diet and exercise and compliance with medication regimes are important factors in determining the outcome for people with hypertension.
Several classes of anti-hypertensive medications are available, including ACE inhibitors, ARB drugs, beta-blockers, diuretics, calcium channel blockers, alpha-blockers, and peripheral vasodilators.
Most anti-hypertensive medications can be used alone or in combination: some are used only in combination; some are preferred over others in certain specific medical situations; and some are not to be used (contraindicated) in other situations.
The goal of therapy for hypertension is to bring the blood pressure down to 140/85 in the general population and to even lower levels in diabetics, African Americans, and people with certain chronic kidney diseases.
Screening, diagnosing, treating, and controlling hypertension early in its course can significantly reduce the risk of developing strokes, heart attacks, or kidney failure.
What are the symptoms of high blood pressure?
What are the symptoms of high blood pressure?
Uncomplicated high blood pressure usually occurs without any symptoms (silently) and so hypertension has been labeled "the silent killer." It is called this because the disease can progress to finally develop any one or more of the several potentially fatal complications of hypertension such as heart attacks or strokes. Uncomplicated hypertension may be present and remain unnoticed for many years, or even decades. This happens when there are no symptoms, and those affected fail to undergo periodic blood pressure screening.
Some people with uncomplicated hypertension, however, may experience symptoms such as headache, dizziness, shortness of breath, and blurred vision. The presence of symptoms can be a good thing in that they can prompt people to consult a doctor for treatment and make them more compliant in taking their medications. Often, however, a person's first contact with a physician may be after significant damage to the end-organs has occurred. In many cases, a person visits or is brought to the doctor or an emergency room with a heart attack, stroke, kidney failure, or impaired vision (due to damage to the back part of the retina). Greater public awareness and frequent blood pressure screening may help to identify patients with undiagnosed high blood pressure before significant complications have developed.
About one out of every 100 (1%) people with hypertension is diagnosed with severe high blood pressure (accelerated or malignant hypertension) at their first visit to the doctor. In these patients, the diastolic blood pressure (the minimum pressure) exceeds 140 mm Hg! Affected persons often experience severe headache, nausea, visual symptoms, dizziness, and sometimes kidney failure. Malignant hypertension is a medical emergency and requires urgent treatment to prevent a stroke (brain damage).
Uncomplicated high blood pressure usually occurs without any symptoms (silently) and so hypertension has been labeled "the silent killer." It is called this because the disease can progress to finally develop any one or more of the several potentially fatal complications of hypertension such as heart attacks or strokes. Uncomplicated hypertension may be present and remain unnoticed for many years, or even decades. This happens when there are no symptoms, and those affected fail to undergo periodic blood pressure screening.
Some people with uncomplicated hypertension, however, may experience symptoms such as headache, dizziness, shortness of breath, and blurred vision. The presence of symptoms can be a good thing in that they can prompt people to consult a doctor for treatment and make them more compliant in taking their medications. Often, however, a person's first contact with a physician may be after significant damage to the end-organs has occurred. In many cases, a person visits or is brought to the doctor or an emergency room with a heart attack, stroke, kidney failure, or impaired vision (due to damage to the back part of the retina). Greater public awareness and frequent blood pressure screening may help to identify patients with undiagnosed high blood pressure before significant complications have developed.
About one out of every 100 (1%) people with hypertension is diagnosed with severe high blood pressure (accelerated or malignant hypertension) at their first visit to the doctor. In these patients, the diastolic blood pressure (the minimum pressure) exceeds 140 mm Hg! Affected persons often experience severe headache, nausea, visual symptoms, dizziness, and sometimes kidney failure. Malignant hypertension is a medical emergency and requires urgent treatment to prevent a stroke (brain damage).
The metabolic syndrome and obesity
The metabolic syndrome and obesity
Genetic factors play a role in the constellation of findings that make up the "metabolic syndrome." Individuals with the metabolic syndrome have insulin resistance and a tendency to have type 2 diabetes mellitus (non-insulin-dependent diabetes).
Obesity, especially associated with a marked increase in abdominal girth, leads to high blood sugar (hyperglycemia), elevated blood lipids (fats), vascular inflammation, endothelial dysfunction (abnormal reactivity of the blood vessels), and hypertension all leading to premature atherosclerotic vascular disease. The American Obesity Association states the risk of developing hypertension is five to six times greater in obese Americans, age 20 to 45, compared to non-obese individuals of the same age. The American Journal of Clinical Nutrition reported in 2005 that waist size was a better predictor of a person's blood pressure than body mass index (BMI). Men should strive for a waist size of 35 inches or under and women 33 inches or under. The epidemic of obesity in the United States contributes to hypertension in children, adolescents, and adults.
Genetic factors play a role in the constellation of findings that make up the "metabolic syndrome." Individuals with the metabolic syndrome have insulin resistance and a tendency to have type 2 diabetes mellitus (non-insulin-dependent diabetes).
Obesity, especially associated with a marked increase in abdominal girth, leads to high blood sugar (hyperglycemia), elevated blood lipids (fats), vascular inflammation, endothelial dysfunction (abnormal reactivity of the blood vessels), and hypertension all leading to premature atherosclerotic vascular disease. The American Obesity Association states the risk of developing hypertension is five to six times greater in obese Americans, age 20 to 45, compared to non-obese individuals of the same age. The American Journal of Clinical Nutrition reported in 2005 that waist size was a better predictor of a person's blood pressure than body mass index (BMI). Men should strive for a waist size of 35 inches or under and women 33 inches or under. The epidemic of obesity in the United States contributes to hypertension in children, adolescents, and adults.
Coarctation of the aorta
Coarctation of the aorta
Coarctation of the aorta is a rare hereditary disorder that is one of the most common causes of hypertension in children. This condition is characterized by a narrowing of a segment of the aorta, the main large artery coming from the heart. The aorta delivers blood to the arteries that supply all of the body's organs, including the kidneys.
The narrowed segment (coarctation) of the aorta generally occurs above the renal arteries, which causes a reduced blood flow to the kidneys. This lack of blood to the kidneys prompts the renin-angiotensin-aldosterone hormonal system to elevate the blood pressure. Treatment of the coarctation is usually the surgical correction of the narrowed segment of the aorta. Sometimes, balloon angioplasty (as described above for renal artery stenosis) can be used to widen (dilate) the coarctation of the aorta.
Coarctation of the aorta is a rare hereditary disorder that is one of the most common causes of hypertension in children. This condition is characterized by a narrowing of a segment of the aorta, the main large artery coming from the heart. The aorta delivers blood to the arteries that supply all of the body's organs, including the kidneys.
The narrowed segment (coarctation) of the aorta generally occurs above the renal arteries, which causes a reduced blood flow to the kidneys. This lack of blood to the kidneys prompts the renin-angiotensin-aldosterone hormonal system to elevate the blood pressure. Treatment of the coarctation is usually the surgical correction of the narrowed segment of the aorta. Sometimes, balloon angioplasty (as described above for renal artery stenosis) can be used to widen (dilate) the coarctation of the aorta.
Adrenal gland tumors
Adrenal gland tumors
Two rare types of tumors of the adrenal glands are less common, secondary causes of hypertension. The adrenal glands sit right on top of the kidneys. Both of these tumors produce excessive amounts of adrenal hormones that cause high blood pressure. These tumors can be diagnosed from blood tests, urine tests, and imaging studies of the adrenal glands. Surgery is often required to remove these tumors or the adrenal gland (adrenalectomy), which usually relieves the hypertension.
One of the types of adrenal tumors causes a condition that is called primary hyperaldosteronism because the tumor produces excessive amounts of the hormone aldosterone. In addition to the hypertension, this condition causes the loss of excessive amounts of potassium from the body into the urine, which results in a low level of potassium in the blood. Hyperaldosteronism is generally first suspected in a person with hypertension when low potassium is also found in the blood. (Also, certain rare genetic disorders affecting the hormones of the adrenal gland can cause secondary hypertension.)
The other type of adrenal tumor that can cause secondary hypertension is called a pheochromocytoma. This tumor produces excessive catecholamines, which include several adrenaline-related hormones. The diagnosis of a pheochromocytoma is suspected in individuals who have sudden and recurrent episodes of hypertension that are associated with flushing of the skin, rapid heart beating (palpitations), and sweating, in addition to the symptoms associated with high blood pressure.
Two rare types of tumors of the adrenal glands are less common, secondary causes of hypertension. The adrenal glands sit right on top of the kidneys. Both of these tumors produce excessive amounts of adrenal hormones that cause high blood pressure. These tumors can be diagnosed from blood tests, urine tests, and imaging studies of the adrenal glands. Surgery is often required to remove these tumors or the adrenal gland (adrenalectomy), which usually relieves the hypertension.
One of the types of adrenal tumors causes a condition that is called primary hyperaldosteronism because the tumor produces excessive amounts of the hormone aldosterone. In addition to the hypertension, this condition causes the loss of excessive amounts of potassium from the body into the urine, which results in a low level of potassium in the blood. Hyperaldosteronism is generally first suspected in a person with hypertension when low potassium is also found in the blood. (Also, certain rare genetic disorders affecting the hormones of the adrenal gland can cause secondary hypertension.)
The other type of adrenal tumor that can cause secondary hypertension is called a pheochromocytoma. This tumor produces excessive catecholamines, which include several adrenaline-related hormones. The diagnosis of a pheochromocytoma is suspected in individuals who have sudden and recurrent episodes of hypertension that are associated with flushing of the skin, rapid heart beating (palpitations), and sweating, in addition to the symptoms associated with high blood pressure.
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